There are suggestive data with indicate the link of testosterone levels with specific cognitive abilities in humans. As soon as during intrauterine development, testosterone is supposed to influence to organization of fetal specific brain structures. This influence is permanent and it is reflected in cognitive abilities during prepubetal period. In puberty, the testosterone level rapidly increases mainly in boys and it appears to influence the definitive development of cognitive functions. In this paper, results of the first four years of our logitudinal study are presented. Salivary testosterone levels in children were determined, and their effect on spatial ability was studied. Radioimmunoanalytical method of testosterone determination in saliva was developed, since saliva reflects free fraction of testosterone directly available for uptake by receptors in the central nervous system. The sampling of saliva is non-invasive and unstressful, which is important for relevant evaluation of cognitive performance. One hundred and forty-seven children (78 boys and 69 girls) at the ae of 8 to 12 were examined. The data received from intellectually gifted children attending the School for gifted children in Bratislava (100 measurements) were compared with the data received from age-matched children attending randomly chosen elementary schools (151 measurements). Lower salivary testosterone levels were found in intellectually gifted children of both sexes, and negative relationship between testosterone levels and cognitive abilities in preadolescent children was observed.